Posts tagged brain structure
Articles and news from the latest research reports.
A New Window of Opportunity to Prevent Cardiovascular and Cerebrovascular Diseases
Future prevention and treatment strategies for vascular diseases may lie in the evaluation of early brain imaging tests long before heart attacks or strokes occur, according to a systematic review conducted by a team of cardiologists, neuroscientists, and psychiatrists from Icahn School of Medicine at Mount Sinai and published in the October issue of JACC Cardiovascular Imaging.
For the review, Mount Sinai researchers examined all relevant brain imaging studies conducted over the last 33 years. They looked at studies that used every available brain imaging modality in patients with vascular disease risk factors but no symptoms that would lead to a diagnosis of diseased blood vessels (vascular disease) in the heart or brain, or periphery (e.g. arms and legs).
The review demonstrates that patients with high blood pressure, diabetes, obesity, high cholesterol, smoking, or metabolic syndrome, but no symptoms, still had visible signs on their neuroimaging scans of structural and functional brain changes long before the development of any events related to vascular diseases of the heart (heart attack) or brain (stroke).
"This is the first time we have been able to disentangle the brain effects of vascular disease risk factors from the brain effects of cardiovascular and cerebrovascular disease and/or events after they develop," says the article’s lead author, Joseph I. Friedman, MD, Associate Professor in the Departments of Psychiatry and Neuroscience at Icahn School of Medicine at Mount Sinai. "Moreover, subtle cognitive impairment is an important clinical manifestation of these vascular disease risk factor-related brain imaging changes in these otherwise healthy persons."
Dr. Friedman added that, because diminished cognitive capacity adversely impacts a person’s ability to benefit from treatment for these medical conditions, early identification of these brain changes may “present a new window of opportunity” for doctors to intervene early and improve prevention of advancement from vascular disease risk factors to established cardiovascular and cerebrovascular diseases. His team is currently testing these hypotheses in ongoing studies at Mount Sinai.
"Patients need to start today to control their vascular risk factors, otherwise their brains may forever harbor physical changes leading to devastating heart and vascular conditions impacting their future overall health and even cognitive decline causing diseases like dementia or when it exists it can accelerate Alzheimer’s," says study author, Valentin Fuster, MD, PhD, Director of Mount Sinai Heart, Physician-in-Chief of The Mount Sinai Hospital, and Chief of the Division of Cardiology at Icahn School of Medicine at Mount Sinai. "Our publication raises the possibility that these early brain changes are major warning signs of what the future may hold for these asymptomatic patients. These high risk patients, along with their doctors, hold the power to modify their daily vascular risk factors to help halt the future course of the manifestation of their potentially looming cardiovascular diseases."
"We hope our publication serves as a primer for cardiologists and other doctors interpreting the early neuroimaging data of their patients who may be high risk for vascular disease," says senior article author Jagat Narula, MD, PhD, Director of Cardiovascular Imaging, Professor of Medicine and Philip J. and Harriet L. Goodhart Chair in Cardiology at Icahn School of Medicine at Mount Sinai. "These subtle brain changes are clues to us physicians that our patients need to start to lower their vascular risk factors always and way before symptoms or a cardiac or brain event happens. This simple step to lower vascular risk factors can have huge impacts on global prevention efforts of cardiovascular diseases."
Researchers identified the following impact of key vascular risk factors on the structural and functional brain health of asymptomatic patients:
- Hypertension is associated with globally appreciable brain volume reductions,
connecting brain fiber abnormalities, reduced brain blood flow, and alterations in the normal pattern of synchronized brain activity between different regions. - Diabetes is associated with connecting brain fiber abnormalities, reduced brain blood flow, and alterations in the normal pattern of synchronized brain activity between different regions.
- Obesity is associated with brain volume reductions, reduced brain blood flow and metabolism.
- High total cholesterol and LDL cholesterol are associated with brain volume reductions, and connecting brain fiber abnormalities. In addition, high triglycerides is associated with reduced brain blood flow, and high total cholesterol is associated with reduced brain metabolism.
- Smoking is associated with brain volume reductions, and alterations of the normal pattern of blood flow. In addition, it causes reduced MAO B (Monoamine Oxidase B) which metabolizes dopamine, the neurotransmitter chemical that controls the brain’s reward and pleasure zones.
- Metabolic Syndrome is associated with a greater burden of silent brain infarcts (SBIs), visible only on MRI, which represents subclinical cerebrovascular disease. In addition, it is associated with connecting brain fiber abnormalities, and alterations in the normal pattern of synchronized brain activity between different regions.
(Source: mountsinai.org)
Mining big data yields Alzheimer’s discovery
Scientists at The University of Manchester have used a new way of working to identify a new gene linked to neurodegenerative diseases such as Alzheimer’s. The discovery fills in another piece of the jigsaw when it comes to identifying people most at risk of developing the condition.
Researcher David Ashbrook and colleagues from the UK and USA used two of the world’s largest collections of scientific data to compare the genes in mice and humans. Using brain scans from the ENIGMA Consortium and genetic information from The Mouse Brain Library, he was able to identify a novel gene, MGST3 that regulates the size of the hippocampus in both mouse and human, which is linked to a group of neurodegenerative diseases. The study has just been published in the journal BMC Genomics.
David, who works in Dr Reinmar Hager’s lab at the Faculty of Life Sciences, says: “There is already the ‘reserve hypothesis’ that a person with a bigger hippocampus will have more of it to lose before the symptoms of Alzheimer’s are spotted. By using ENIGMA to look at hippocampus size in humans and the corresponding genes and then matching those with genes in mice from the BXD system held in the Mouse Brain Library database we could identify this specific gene that influences neurological diseases.”
He continues: “Ultimately this could provide another biomarker in the toolkit for identifying those at greatest risk of developing diseases such as Alzheimer’s.”
Dr Hager, senior author of the study, says: “What is critical about this research is that we have not only been able to identify this specific gene but also the networks it uses to influence a disease like Alzheimer’s. We believe this information will be incredibly useful for future studies looking at treatments and preventative measures.”
The ENIGMA Consortium is led by Professor Paul Thompson based at the University of California, Los Angeles, and contains brain images and gene information from nearly 25,000 subjects. The Mouse Brain Library, established by Professor Robert Williams based at the University of Tennessee Health Science Center, contains data on over 10,000 brains and numerical data from just over 20,000 mice.
David explains why combining the information held by both databases is so useful: “The key advantage of working this way is that it is much easier to identify a genetic variant in mice as they live in such controlled environments. By taking the information from mice and comparing it to human gene information we can identify the same variant much more quickly.”
And David thinks this way of working will be used more often in the future: “We are living in a big data world thanks to the likes of the Human Genome Project and post-genome technologies. A lot of that information is now widely shared so by mining what we already know we can learn so much more, advancing our knowledge of diseases and ultimately improving detection and treatment.”
(Source: manchester.ac.uk)
(Image caption: 3D image of the hippocampus of a rat. Credit: M. Pyka)
People who wish to know how memory works are forced to take a glimpse into the brain. They can now do so without bloodshed: RUB researchers have developed a new method for creating 3D models of memory-relevant brain structures. They published their results in the trade journal “Frontiers in Neuroanatomy”.
Sea Horse gave the hippocampus the name
The way neurons are interconnected in the brain is very complicated. This holds especially true for the cells of the hippocampus. It is one of the oldest brain regions and its form resembles a sea horse (hippocampus in Latin). The hippocampus enables us to navigate space securely and to form personal memories. So far, the anatomic knowledge of the networks inside the hippocampus and its connection to the rest of the brain has left scientists guessing which information arrived where and when.
Signals spread through the brain
Accordingly, Dr Martin Pyka and his colleagues from the Mercator Research Group have developed a method which facilitates the reconstruction of the brain’s anatomic data as a 3D model on the computer. This approach is quite unique, because it enables automatic calculation of the neural interconnection on the basis of their position inside the space and their projection directions. Biologically feasible network structures can thus be generated more easily than it used to be the case with the method available to date. Deploying 3D models, the researchers use this technique to monitor the way neural signals spread throughout the network time-wise. They have, for example, found evidence that the hippocampus’ form and size could explain why neurons in those networks fire in certain frequencies.
Information become memories
In future, this method may help us understand how animals, for example, combine various information to form memories within the hippocampus, in order to memorise food sources or dangers and to remember them in certain situations.
Study suggests neurobiological basis of human-pet relationship
It has become common for people who have pets to refer to themselves as “pet parents,” but how closely does the relationship between people and their non-human companions mirror the parent-child relationship? A small study from a group of Massachusetts General Hospital (MGH) researchers makes a contribution to answering this complex question by investigating differences in how important brain structures are activated when women view images of their children and of their own dogs. Their report is being published in the open-access journal PLOS ONE.
“Pets hold a special place in many people’s hearts and lives, and there is compelling evidence from clinical and laboratory studies that interacting with pets can be beneficial to the physical, social and emotional wellbeing of humans,” says Lori Palley, DVM, of the MGH Center for Comparative Medicine, co-lead author of the report. “Several previous studies have found that levels of neurohormones like oxytocin – which is involved in pair-bonding and maternal attachment – rise after interaction with pets, and new brain imaging technologies are helping us begin to understand the neurobiological basis of the relationship, which is exciting.”
In order to compare patterns of brain activation involved with the human-pet bond with those elicited by the maternal-child bond, the study enrolled a group of women with at least one child aged 2 to 10 years old and one pet dog that had been in the household for two years or longer. Participation consisted of two sessions, the first being a home visit during which participants completed several questionnaires, including ones regarding their relationships with both their child and pet dog. The participants’ dog and child were also photographed in each participants’ home.
The second session took place at the Athinoula A. Martinos Center for Biomedical Imaging at MGH, where functional magnetic resonance imaging (fMRI) – which indicates levels of activation in specific brain structures by detecting changes in blood flow and oxygen levels – was performed as participants lay in a scanner and viewed a series of photographs. The photos included images of each participant’s own child and own dog alternating with those of an unfamiliar child and dog belonging to another study participant. After the scanning session, each participant completed additional assessments, including an image recognition test to confirm she had paid close attention to photos presented during scanning, and rated several images from each category shown during the session on factors relating to pleasantness and excitement.
Of 16 women originally enrolled, complete information and MR data was available for 14 participants. The imaging studies revealed both similarities and differences in the way important brain regions reacted to images of a woman’s own child and own dog. Areas previously reported as important for functions such as emotion, reward, affiliation, visual processing and social interaction all showed increased activity when participants viewed either their own child or their own dog. A region known to be important to bond formation – the substantia nigra/ventral tegmental area (SNi/VTA) – was activated only in response to images of a participant’s own child. The fusiform gyrus, which is involved in facial recognition and other visual processing functions, actually showed greater response to own-dog images than own-child images.
“Although this is a small study that may not apply to other individuals, the results suggest there is a common brain network important for pair-bond formation and maintenance that is activated when mothers viewed images of either their child or their dog,” says Luke Stoeckel, PhD, MGH Department of Psychiatry, co-lead author of the PLOS One report. “We also observed differences in activation of some regions that may reflect variance in the evolutionary course and function of these relationships. For example, like the SNi/VTA, the nucleus accumbens has been reported to have an important role in pair-bonding in both human and animal studies. But that region showed greater deactivation when mothers viewed their own-dog images instead of greater activation in response to own-child images, as one might expect. We think the greater response of the fusiform gyrus to images of participants’ dogs may reflect the increased reliance on visual than verbal cues in human-animal communications.”
Co-author Randy Gollub, MD, PhD, of MGH Psychiatry adds, “Since fMRI is an indirect measure of neural activity and can only correlate brain activity with an individual’s experience, it will be interesting to see if future studies can directly test whether these patterns of brain activity are explained by the specific cognitive and emotional functions involved in human-animal relationships. Further, the similarities and differences in brain activity revealed by functional neuroimaging may help to generate hypotheses that eventually provide an explanation for the complexities underlying human-animal relationships.”
The investigators note that further research is needed to replicate these findings in a larger sample and to see if they are seen in other populations – such as women without children, fathers and parents of adopted children – and in relationships with other animal species. Combining fMRI studies with additional behavioral and physiological measures could obtain evidence to support a direct relationship between the observed brain activity and the purported functions.
(Image: Fotolia)
Brain scans reveal ‘grey matter’ differences in media multitaskers
Simultaneously using mobile phones, laptops and other media devices could be changing the structure of our brains, according to new University of Sussex research.
A study published today (24 September) in PLOS ONE reveals that people who frequently use several media devices at the same time have lower grey-matter density in one particular region of the brain compared to those who use just one device occasionally.
The research supports earlier studies showing connections between high media-multitasking activity and poor attention in the face of distractions, along with emotional problems such as depression and anxiety.
But neuroscientists Kep Kee Loh and Dr Ryota Kanai point out that their study reveals a link rather than causality and that a long-term study needs to be carried out to understand whether high concurrent media usage leads to changes in the brain structure, or whether those with less-dense grey matter are more attracted to media multitasking.
The researchers at the University of Sussex’s Sackler Centre for Consciousness Science used functional magnetic resonance imaging (fMRI) to look at the brain structures of 75 adults, who had all answered a questionnaire regarding their use and consumption of media devices, including mobile phones and computers, as well as television and print media.
They found that, independent of individual personality traits, people who used a higher number of media devices concurrently also had smaller grey matter density in the part of the brain known as the anterior cingulate cortex (ACC), the region notably responsible for cognitive and emotional control functions.
Kep Kee Loh says: “Media multitasking is becoming more prevalent in our lives today and there is increasing concern about its impacts on our cognition and social-emotional well-being. Our study was the first to reveal links between media multitasking and brain structure.”
Scientists have previously demonstrated that brain structure can be altered upon prolonged exposure to novel environments and experience. The neural pathways and synapses can change based on our behaviours, environment, emotions, and can happen at the cellular level (in the case of learning and memory) or cortical re-mapping, which is how specific functions of a damaged brain region could be re-mapped to a remaining intact region.
Other studies have shown that training (such as learning to juggle, or taxi drivers learning the map of London) can increase grey-matter densities in certain parts of the brain.
“The exact mechanisms of these changes are still unclear,” says Kep Kee Loh. “Although it is conceivable that individuals with small ACC are more susceptible to multitasking situations due to weaker ability in cognitive control or socio-emotional regulation, it is equally plausible that higher levels of exposure to multitasking situations leads to structural changes in the ACC. A longitudinal study is required to unambiguously determine the direction of causation.”
(Source: sussex.ac.uk)
Study links physical activity in older adults to brain white-matter integrity
Like everything else in the body, the white-matter fibers that allow communication between brain regions also decline with age. In a new study, researchers found a strong association between the structural integrity of these white-matter tracts and an older person’s level of daily activity – not just the degree to which he or she engaged in moderate or vigorous exercise, but also whether the person was sedentary the rest of the time.
The study, reported in the journal PLOS ONE, tracked physical activity in 88 healthy but “low-fit” participants aged 60 to 78. The participants agreed to wear accelerometers during most of their waking hours over the course of a week, and also submitted to brain imaging.
“To our knowledge, this is the first study of its kind that uses an objective measure of physical activity along with multiple measures of brain structure,” said University of Illinois postdoctoral researcher Agnieszka Burzynska, who conducted the research with U. of I. Beckman Institute director Arthur Kramer and kinesiology and community health professor Edward McAuley.
Most studies ask subjects to describe how much physical activity they get, which is subjective and imprecise, Burzynska said. The accelerometer continuously tracks a person’s movement, “so it’s not what they say they do or what they think they do, but we have measured what they are actually doing,” she said.
The researchers assumed that participants’ activity levels over a week accurately reflected their overall engagement, or lack of engagement, in physical activity.
The study also relied on two types of brain imaging. The first, diffusion tensor imaging, offers insight into the structural integrity of a tissue by revealing how water is diffused in the tissue. The second method looks for age-related changes in white matter, called lesions. Roughly 95 percent of adults aged 65 and older have such lesions, Burzynska said. While they are a normal part of aging, their early onset or rapid accumulation may spell trouble, she said.
The team found that the brains of older adults who regularly engaged in moderate-to-vigorous exercise generally “showed less of the white-matter lesions,” Burzynska said.
The association between physical activity and white-matter structural integrity was region-specific, the researchers reported. Older adults who engaged more often in light physical activity had greater structural integrity in the white-matter tracts of the temporal lobes, which lie behind the ears and play a key role in memory, language, and the processing of visual and auditory information.
In contrast, those who spent more time sitting had lower structural integrity in the white-matter tracts connecting the hippocampus, “a structure crucial for learning and memory,” Burzynska said.
“This relationship between the integrity of tracts connecting the hippocampus and sedentariness is significant even when we control for age, gender and aerobic fitness,” she said. “It suggests that the physiological effect of sitting too much, even if you still exercise at the end of the day for half an hour, will have a detrimental effect on your brain.”
The findings suggest that engaging in physical activity and avoiding a sedentary lifestyle are both important for brain health in older age, Burzynska said.
“We hope that this will encourage people to take better care of their brains by being more active,” she said.
Brain Structure of Kidney Donors May Make Them More Altruistic
That’s the finding of a study published in today’s Proceedings of the National Academy of Sciences (PNAS) by Georgetown researchers.
Georgetown College psychology professor Abigail Marsh worked with John VanMeter, director of Center for Functional and Molecular Imaging at Georgetown University Medical Center, to scan the brains of 19 altruistic kidney donors.
More Sensitive to Distress
“The results of brain scans and behavioral testing suggests that these donors have some structural and functional brain differences that may make them more sensitive, on average, to other people’s distress,” Marsh explains.
The Georgetown researchers used functional MRI to record the neural activity of the kidney donors and 20 control subjects who had never donated an organ as they viewed faces with fearful, angry or neutral expressions.
Underlying Neural Basis
In the right amygdala, an emotion-sensitive brain region, altruists displayed greater neural activity while viewing fearful expressions than did control subjects.
When asked to identify the emotional expressions presented in the face images, altruists recognized fearful facial expressions relatively more accurately than the control subjects.
“The brain scans revealed that the right amygdala volume of altruists is larger than that of non-altruists,” Marsh says. “The findings suggest that individual differences in altruism may have an underlying neural basis.”
Opposite From Psychopaths?
These findings dovetail with previous research by the professor showing structural and functional brain differences that appear to make people with psychopathic traits less sensitive to others’ fear and distress.
These differences include amygdalas that are smaller and less responsive to fearful expressions. People who are unusually altruistic may therefore be the opposite in some ways from people who are psychopathic.
To find kidney donors, the researchers reached out to the Washington Regional Transplant Community (WRTC), a federally designated organ procurement organizations.
A Donor’s Story
Harold Mintz, former northern Virginian who volunteered with WRTC and agreed to participate in the Georgetown study, donated a kidney to an anonymous stranger he later learned was an Ethiopian refugee who had settled in Washington, D.C.
Mintz, who now lives in California and speaks to high school students about his 2000 donation, says a series of events over time led him to supply the kidney, including his father dying of cancer diagnosed too late at the age of 56.
One Valentine’s Day in 1988, Mintz and his wife were shopping separately for presents and Mintz noticed parents in a mall with a sign saying “Please Save Our Daughter’s Life.” He walked past them, then turned around and asked what they needed. It turned out the daughter had leukemia and needed a bone marrow transplant.
The couple decided to forget about the holiday and donated blood to see if either of them were a match. But no match was found and Mintz later noticed the daughter’s obituary in the newspaper.
Stories Taken to Heart
Mintz also was surprised to hear that although the couple’s daughter had just died, they thanked everyone who tried to help and expressed hope that they might help someone else.
“All these stories just kind of stuck inside my head and every time I’d see a story about a medical story of distress, it would just kind of get put away in a file inside my heart,” Mintz says.
Marsh notes that kidney disease is now the eighth-leading cause of death in the U.S., and that living kidney donations are the best hope for restoring people to health who have kidney disease.
“Dr. Marsh’s work is a great example of how fMRI can be used to provide insight into how differences in the brain’s response can lead individuals to perform such magnanimous acts,” VanMeter says.
Grey matter matters when measuring our tolerance of risk
There is a link between our brain structure and our tolerance of risk, new research suggests.
Dr Agnieszka Tymula, an economist at the University of Sydney, is one of the lead authors of a new study that identifies what might be considered the first stable ‘biomarker’ for financial risk-attitudes.
Using a whole-brain analysis, Dr Tymula and international collaborators found that the grey matter volume of a region in the right posterior parietal cortex was significantly predictive of individual risk attitudes. Men and women with higher grey matter volume in this region exhibited less risk aversion.
"Individual risk attitudes are correlated with the grey matter volume in the posterior parietal cortex suggesting existence of an anatomical biomarker for financial risk-attitude," said Dr Tymula.
This means tolerance of risk “could potentially be measured in billions of existing medical brain scans.”
But she has cautioned against making a causal link between brain structure and behaviour. More research will be needed to establish whether structural changes in the brain lead to changes in risk attitude or whether that individual’s risky choices alter his or her brain structure - or both.
"The findings fit nicely with our previous findings on risk attitude and ageing. In our Proceedings of the National Academy of Sciences 2013 paper we found that as people age they become more risk averse,” she said.
"From other work we know that cortex thins substantially as we age. It is possible that changes in risk attitude over lifespan are caused by thinning of the cortex."
The findings are published in the September 10 issue of The Journal of Neuroscience.
Brain structure could predict risky behavior
Some people avoid risks at all costs, while others will put their wealth, health, and safety at risk without a thought. Researchers at Yale School of Medicine have found that the volume of the parietal cortex in the brain could predict where people fall on the risk-taking spectrum.
Led by Ifat Levy, assistant professor in comparative medicine and neurobiology at Yale School of Medicine, the team found that those with larger volume in a particular part of the parietal cortex were willing to take more risks than those with less volume in this part of the brain. The findings are published in the Sept. 10 issue of the Journal of Neuroscience.
Although several cognitive and personality traits are reflected in brain structure, there has been little research linking brain structure to economic preferences. Levy and her colleagues sought to examine this question in their study.
Study participants included young adult men and women from the northeastern United States. Participants made a series of choices between monetary lotteries that varied in their degree of risk, and the research team conducted standard anatomical MRI brain scans. The results were first obtained in a group of 28 participants, and then confirmed in a second, independent, group of 33 participants.
“Based on our findings, we could, in principle, use millions of existing medical brains scans to assess risk attitudes in populations,” said Levy. “It could also help us explain differences in risk attitudes based in part on structural brain differences.”
Levy cautions that the results do not speak to causality. “We don’t know if structural changes lead to behavioral changes or vice-versa,” she said.
Levy and her team had previously shown that risk aversion increases as people age, and we scientists also know that the cortex thins substantially with age. “It could be that this thinning explains the behavioral changes; we are now testing that possibility,” said Levy, who also notes that more studies in wider populations are needed.
Socioeconomic status and structural brain development
Recent advances in neuroimaging methods have made accessible new ways of disentangling the complex interplay between genetic and environmental factors that influence structural brain development. In recent years, research investigating associations between socioeconomic status (SES) and brain development have found significant links between SES and changes in brain structure, especially in areas related to memory, executive control, and emotion. This review focuses on studies examining links between structural brain development and SES disparities of the magnitude typically found in developing countries. We highlight how highly correlated measures of SES are differentially related to structural changes within the brain.